Amino-grafted Biochar as a Novel Photocatalyst for degradation of high concentration dye.

Photocatalytic degradation of organic pollution by biochar was a sustainable strategy for waste water remediation, nevertheless, it still suffers drawbacks like low efficiency due to the poor photocatalytic properties of pristine biochar. Herein, amino groups were grafted on the edge sites/defects of biochar by Friedel-Crafts acylation to enhance the degradation of high concentration dye solutions. The results suggested that the amino groups played an important role in imparting photocatalytic properties to biochar. Owing to the strong Lewis basicity and electron-donating ability of amino groups, their interaction with oxygen-containing functional groups/aromatic structures in biochar was improved, which enhanced the electron exchange ability of biochar under visible light irradiation, resulting in excellent degradation performances of high concentration RhB (∼10 times faster than ungrafted biochar). In this work, amino-grafted garlic peel biochar delivered a new idea for the future direction of biochar-based photocatalysis in wastewater remediation.

Effects of biogas slurry on hydrothermal carbonization of digestate: Synergistic valorization of hydrochars and aqueous phase.

In this study, livestock manure digestate (LMD) was used as feedstock for hydrothermal carbonization (HTC) at different temperature (180-260 °C) and residence time (0-4 h). Nutrient flow and distribution during the HTC process were evaluated by comparing the effects of livestock manure biogas slurry (LBS) and ultrapure water (UW) to determine the optimal reaction conditions for the synergistic production and application of hydrochars (HC) and aqueous phases (AP). Compared with UW, the HC yields derived from LBS as solvent were increased by 27.05-38.24% under the same conditions. The C content, high heating value (HHV), and energy densification of HC obtained from LMD and UW were higher than those obtained from LMD and LBS, and the ash content was lower. While, LBS circumstance improved the porosity, N content and some trace elements e.g. Ca, Fe and Mg in HC that showed excellent fertility potential. In addition, the recovery rate of K, TOC, NH4+-N, and TN concentrations in AP were significantly higher in the LBS circumstance than in UW. The results show that the addition of UW is more favorable for fuel generation, and the HC obtained from LMD and UW at 220 °C has the potential to be used as a fuel. Whereas, the addition of LBS enhanced the potential of HC and AP for agricultural applications simultaneously. It is recommended to use HC and AP obtained from LMD and LBS at 240 °C for using as fertilizer.

Surface-sealing encapsulation of phosphotungstic acid in microporous UiO-66 as a bifunctional catalyst for transfer hydrogenation of levulinic acid to γ-valerolactone.

The efficient production of γ-valerolactone (GVL) from renewable lignocellulose that is synthesized in plants by photosynthesis to replace the declining fossil resources conforms to the principles of circular economy. Compared to direct hydrogenation by H2 molecules, catalytic transfer hydrogenation (CTH) of levulinic acid (LA) and/or its esters to GVL with organic alcohols as a hydrogen source is a much milder route. The synergistic catalysis between Lewis and Brønsted acids is indispensable in the CTH process. Considering that unsaturated coordinated Zr species could act as Lewis acid sites and phosphotungstic acid (PTA) could dissociate protons as Brønsted acid sites, UiO-66 (Zr) was thus "acidified" by encapsulating PTA in its channels to tune the ratio of Brønsted to Lewis acid sites as a bifunctional catalyst so as to better understand the catalytic structure-performance relationship in the CTH process. To address the dilemma of encapsulated PTA that is prone to leach, a rapid surface sealing strategy was adopted to establish a polyimide (PI) coating over the surface of UiO-66 introducing a space confinement effect via an anhydride-amine coupling reaction. The as-synthesized PTA/UiO-66@PI catalyst exhibited 100% of LA conversion, a 93.2% of GVL yield and high recyclability for at least five consecutive cycles. Moreover, a reaction pathway followed by esterification, hydrogenation and dealcoholization as well as a catalytic hydrogenation mechanism based on intermolecular hydride ß-H transfer were proposed. Current work not only provides a high-performance and high-stability catalytic system to selectively produce GVL from LA or its esters, but also sheds light on the catalytic mechanism of the CTH process at the molecular level.

Cu/SiO2 synthesized with HKUST-1 as precursor: high ratio of Cu+/(Cu+ + Cu0) and rich oxygen defects for efficient catalytic hydrogenation of furfural to 2-methyl furan.

Cu/SiO2 is one of the most promising catalysts for the furfural (FF) hydrogenation reaction but suffers from the difficulty of tailoring the microstructure and surface properties. Herein, we developed a MOF-derived Cu/SiO2 catalyst (Cu/SiO2-MOF) for FF hydrogenation to 2-methyl furan (2-MF). In comparison with Cu/SiO2 catalysts prepared from ammonia evaporation (Cu/SiO2-AE) and traditional impregnation (Cu/SiO2-TI), the copper species in Cu/SiO2-MOF could not only be anchored on the silica surface via forming Cu-O-Si bonds but also exposed many more active sites. In this way, a higher ratio of Cu+/(Cu+ + Cu0) and richer oxygen defects were constructed via strong metal-support interactions, which were responsible for the superior catalytic performance. In addition, it was found that the solvent effect on product distribution played an important role in adjusting the selectivity to 2-MF and cyclopentanone (CPO). The present work not only provides a deep insight into the catalytic mechanism of Cu/SiO2-MOF for the FF hydrogenation reaction but also sheds light on the design and synthesis of highly efficient catalysts for other heterogeneous catalysis fields.

Lignin and spent bleaching clay into mono-aromatic hydrocarbons by a cascade dual catalytic pyrolysis system: Critical role of spent bleaching clay.

In the present study, a cascade dual catalytic system was used for the co-pyrolysis of lignin with spent bleaching clay (SBC) to efficiently produce mono-aromatic hydrocarbon (MAHs). The cascade dual catalytic system is composed of calcined SBC (CSBC) and HZSM-5. In this system, SBC not only acts as a hydrogen donor and catalyst in the co-pyrolysis process, but is also used as a primary catalyst in the cascade dual catalytic system after recycling the pyrolysis residues. The effects of different influencing factors (i.e., temperature, CSBC-to-HZSM-5 ratio, and raw materials-to-catalyst ratio) on the system were explored. It was observed that, when the temperature was 550 °C, the CSBC-to-HZSM-5 ratio was 1:1, and when the raw materials-to-catalyst ratio was 1:2, the highest bio-oil yield was 21.35 wt%. The relative MAHs content in bio-oil was 73.34 %, whereas the relative polycyclic aromatic hydrocarbons (PAHs) content was 23.01 %. Meanwhile, the introduction of CSBC inhibited the generation of graphite-like coke as indicated by HZSM-5. This study realizes the full resource utilization of spent bleaching clay and reveals the environmental hazards caused by spent bleaching clay and lignin waste.

Influence of nano-Fe3O4 biochar on the methanation pathway during anaerobic digestion of chicken manure.

Volatile fatty acids and ammonia nitrogen (AN) accumulate during anaerobic digestion (AD) of high N substrates, such as chicken manure (CM), causing decreases in methane yield. Previous research found that the addition of nano-Fe3O4 biochar can alleviate the inhibition caused by acids and ammonia and increase methane production. The mechanism of enhanced methane production in nano-Fe3O4 biochar-mediated AD of CM was explored in depth in this study. The results showed the lowest AN concentration in the control and nano-Fe3O4 biochar addition groups were 8,229.0 mg/L and 7,701.5 mg/L, respectively. Methane yield of volatile solids increased from 92.0 mL/g to 219.9 mL/g in the nano-Fe3O4 biochar treatment, which was attributed to the enrichment of unclassified Clostridiales and Methanosarcina. The mechanism of nano-Fe3O4 biochar in AD of CM under high AN level was to improve methane production by promoting syntrophic acetate oxidation and facilitating direct electron transfer between microorganisms.

Biodiesel production in a magnetically fluidized bed reactor using whole-cell biocatalysts immobilized within ferroferric oxide-polyvinyl alcohol composite beads.

Magnetic whole-cell biocatalysts (MWCBs) constructed by immobilizing Bacillus subtiliscells within ferroferric oxide-polyvinyl alcohol composite beads were developed and employed to transesterify waste frying oil to biodiesel in a magnetically fluidized bed reactor (MFBR). Effective variables including biocatalysts concentration, reactant flow rate, magnetic field intensity and temperature were evaluated to enhance the transesterification. By coupling MFBR with MWCBs, continuous biodiesel production was achieved. Response surface methodology and Box-Behnken design were employed to predict the optimal conditions and the maximum biodiesel yield reached 89.0 ± 0.6% after 48 h under the optimized conditions. Furthermore, MWCBs displayed satisfactory stability and reusability in MFBR and still maintained a biodiesel yield of more than 82.5% after 10 cycles. Lastly, the fuel properties of the obtained biodiesel met the ASTM and EN standards. The present study revealed that the route of producing biodiesel over MWCBs in the MFBR system showed great potential for industrialization.

Self­nitrogen-doped carbon materials derived from microalgae by lipid extraction pretreatment: Highly efficient catalyst for the oxygen reduction reaction.

Biomass-based nitrogen-doped carbon-based material has gradually become a premising metal alternative catalyst for oxygen reduction reaction due to their broad resources, renewable property, and low cost. However, the efficient nitrogen doping is still restricted by their low content and poor conversion efficiency. In this study, self- nitrogen -doped biomass-based carbon materials with high content of nitrogen (27.8% pyridinic-N and 40.3% graphitic-N) and hierarchical pore structure were prepared via lipid extraction pretreatment. The obtained microalgae residue carbon (MRC) catalyst exhibits superior oxygen reduction reaction performance, in terms of more preferable electrode performance and better stability, higher power density in the microbial fuel cells system compared to that of microalgae carbon (MAC). The onset potential of the MRC is 60 mV higher than that of MAC, and the maximum power density of microbial fuel cells (MFCs) with MRC as cathode catalyst reache 412.85 mW m-2. This can be attributed to the fact of that the lipid extraction was not only beneficial to the nitrogen enhancement and oriented conversion but also be conductive to the structure construction. The synergistic effect between active sites and hierarchical structure endows the catalyst excellent ORR performance and good stability in the MFCs system.

The "business" of dentistry: Consumers' (patients') criteria in the selection and evaluation of dental services.

The dimensions of patient-centred care include not only clinical effectiveness and patient safety, but, importantly, the preferences of patients as consumers of healthcare services. A total of 249 participants were included in the study, with a balanced population proportional representation by age, gender, ethnicity and geographic region of New Zealand. An online questionnaire was used to identify participants' decision-making process, and what factors and barriers for participants to seek dental treatment. Cross-tabulations, Spearman correlation analysis and Pearson Chi-Square analysis were used for the statistical analyses. Three most common reasons for visit were check-up (77%), clean (57%) and relief of pain 36%). A desire to treat a perceived problem was the most common encouraging factor to seek dental care. Cost was the most common barrier to seeking dental services. The majority of participants attended a private practice (84%), with convenience of location and referral from professionals the most likely to influence their choice. Participants felt the most important trait a dental practitioner could demonstrate was to discuss treatment options with them before any treatment. Dental check-up, teeth cleaning and relief of pain were the most common reasons for patients to choose dental services. Cost and ethnicity of the consumers had a significant impact on how dental services were perceived and sought. Dental practitioners may need to reorientate how they express value of oral health practice, not just in regard to communication with patients, but also with government funding agencies.

Anaerobic digestion of corn straw pretreated by ultrasonic combined with aerobic hydrolysis.

Corn straw (CS) was pretreated by ultrasonic combined aerobic with biogas slurry as medium for anaerobic digestion (AD), that strengthened the degradation efficiency CS, varied in the composition of digestion slurry, thereby the methane production was increased. Central combinatorial design (CCD) test was used to treat CS at ultrasonic power (200, 400, and 600 W), time (10, 20, and 30 min) and AD for 25 days, at 37 ± 1℃. According to data showed that the pH and volatile fatty acids (VFAs) affected methane production directly. With an ultrasonic power 309 W, time 26 min, it reached the maximum content of VFAs with 16.24 g/L, the cumulative methane production achieved the highest with 198.56 mL/g VS, which was 46.73% higher than unpretreated raw material as CK. Ultrasonic-aerobic hydrolysis pretreatment can obtain higher VFAs and methane production content in a short period of time that is great significance to biogas engineering.

Comparative study on the catalytic steam reforming of biomass pyrolysis oil and its derivatives for hydrogen production.

In order to explore the reforming process of biomass pyrolysis oil in depth, the catalytic steam reforming (SR) of crude bio-oil (BIO) derived from rapid pyrolysis of rice husk and its derivatives for hydrogen production was studied by means of a bench-scale fixed-bed unit combined with the FTIR/TCD technique. The physico-chemical properties and compositions of BIO were determined. Acetic acid (HOAc), ethylene glycol (EG), acetone (ACE) and phenol (PHE) were selected as four representative bio-oil derivatives. Evolution characteristics of H2, CO, CO2 and CH4 during SR of HOAc, EG, ACE, PHE and BIO were revealed and compared. The hydrogen yield increased sharply with reaction time to the peak values of 24.7%, 32.3%, 16.4%, 25.6% and 24.9%, corresponding to HOAc, EG, ACE, PHE and BIO, respectively. After that, the yield of hydrogen exhibited a downward trend, suggesting that the catalyst ability for selective hydrogen production gradually decreased. The H2 yield from EG was the highest, followed by PHE, HOAc, BIO and ACE. The order of CO yields from large to small was EG > HOAc > ACE > BIO ≈ PHE. The percentages of coke deposited on catalyst were arranged in descending order as HOAc > BIO > ACE > PHE > EG. This study could provide more detailed information on the catalytic reforming mechanism of bio-oil on the one hand, and also point out the direction for the improvement of the catalysts, which play a role in ensuring the high yield of H2 while converting CO to H2 through the water gas shift reaction.

Biocomposites from Organic Solid Wastes Derived Biochars: A Review.

The replacement of natural fiber with biochars to prepare biocomposites has attracted widespread attention recently. Biochar has unique properties, including the porous structure, large specific surface area, high thermal stability, good conductivity, renewable and abundant feedstock source, and environmental friendliness, which provide excellent properties, environmental benefits, and low production costs for biochar-based composites. Biocomposites from organic solid waste-derived biochars show good prospects worldwide in terms of positive social, environmental, and economic impacts. This paper reviews current biochars, elucidates the effects of biochars on the characteristics and performance of biochar composites, and points out the challenges and future development prospects of biochar composites.

Anaerobic co-digestion of corn stover and wastewater from hydrothermal carbonation.

This study aimed to investigate the interactions between wastewater of hydrothermal carbonation (W-HTC) and corn stover (CS) during anaerobic co-digestion. The results showed the maximum cumulative methane production of co-digestion was 280.7 ± 3.2 mL/g VS, and it increased by 5.84% and 10.69% compared with mono-digestion of CS and W-HTC, respectively. Increasing the HTC temperature and excess addition of W-HTC inhibits early and middle stage of co-digestion due to toxic organic inhibitors, and the negative effect of phenols is substantially more than furans. The microbial analysis illustrated the addition of W-HTC can promote the growth of Clostridia and Bacteroidia. The growth of Methanomassiliicoccus and Methanosarcina was more vigorous in most of co-digestions, which was positively correlated with methane production. The study concluded methanogenesis can be enhanced by the co-digestion of W-HTC and CS, which provide optimization of process conditions and some reaction mechanism for application of W-HTC in anaerobic digestion.

Effect of pyrolysis temperature on characteristics, chemical speciation and environmental risk of Cr, Mn, Cu, and Zn in biochars derived from pig manure.

The comprehensive analysis of environmental risk for heavy metals in pig manure was essential for optimization of pyrolysis conditions and scientific utilization of pig manure biochars as soil amendment. However, in previous studies, the selected pyrolysis temperature points were limited and temperature interval was large, it's was difficult to accurately verify the effect of pyrolysis temperature on chemical speciation and environmental risk of heavy metals. Therefore, in this study, pig manure was pyrolyzed at 300-700 °C with a small interval of 50 °C to study the effect of pyrolysis temperature on characteristics and environmental risk of Cr, Mn, Cu and Zn in pig manure biochar. Results indicated that the characteristics of biochars (>500 °C) were relatively stable. The biochar obtained at 700 °C exhibited the largest surface area (8.28 m2 g-1) and pore volume (25.17 m3 kg-1), secondly is the biochar derived at 500 °C. The total percentages of exchangeable and acid fraction and reducible fraction decreased from 16.98% to 9.43% for Cr, 85.60% to 65.55% for Mn, 57.26% to 10.61% for Cu, 37.90% to 13.78% for Zn, respectively, suggesting that exchangeable and acid fraction and reducible fraction of Cr, Mn, Cu and Zn in pig manure were transformed into oxidizable and residual fractions after pyrolysis. The leaching rates, risk assessment code and potential ecological risk index values significantly decreased after pyrolysis and presented lower value at 500 and 700 °C. Biochars derived at 300-700 °C conditions posed no phytotoxicity with germination index >80%. Correlation analyses revealed that larger surface area, pore volume and pH values of biochars may help to immobilize heavy metals and reduce bioavailability. These findings demonstrated that bioavailability and toxicity of Cr, Mn, Cu and Zn in pig manure biochar were greatly reduced after pyrolysis and the optimum temperature was 500 °C considering energy cost.

Production of high-density polyethylene biocomposites from rice husk biochar: Effects of varying pyrolysis temperature.

The novelty of this study is to explore the effect of temperature varied biochar on the properties of biochar/polymers composites. Rice husk biochar (RB) samples were prepared at different pyrolysis temperatures and injection molding was used to prepare RB/high-density polyethylene (HDPE) composites. Additionally, ultimate analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), pore structure characteristics, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile properties, and dynamic mechanical analysis (DMA) were used to characterize these RB and RB/HDPE composites samples. The results validated that RB obtained at 600 °C showed the highest carbon content, the most complete pore structure, and the largest specific surface area. Moreover, the thermal studies revealed that the addition of RB improved the thermal stability of HDPE. The best tensile strength (26.25 MPa) and Young's modulus (1.87 GPa) were obtained in 500 °C RB/HDPE composites and 600 °C RB/HDPE composites due to their good physical/mechanical interlocking structures shown in SEM. DMA revealed that the stiffness, elasticity, creep resistance and stress relaxation of the composites were improved by the addition of RB. The utilization of temperature varied biochars in biocomposites is important to manage wastes and optimize the properties of biocomposites in terms of reducing production cost and ensuring environmental safety.

Properties evaluation of biochar/high-density polyethylene composites: Emphasizing the porous structure of biochar by activation.

Activated biochars (AB-0.5, AB-1, AB-1.5, AB-2) prepared under different concentrations of an activating agent were used to manufacturing composites (ABHC-0.5, ABHC-1, ABHC-1.5, ABHC-2) based on high-density polyethylene (HDPE) by compounding and injection molding. Thermal and mechanical properties of the composites were characterized and analyzed. The addition of activated biochars improved the thermal properties of HDPE shown by Differential scanning calorimetry and Thermogravimetric analysis. Additionally, ABHC-0.5 exhibited the best flexural strength (38.66 MPa), flexural modulus (2.46 GPa), tensile strength (32.17 MPa), tensile modulus (1.95 GPa), rigidity, elasticity, creep resistance, and anti-stress relaxation ability due to the best porous structure of AB-0.5. A decrease of mechanical properties was observed in ABHC-1, ABHC-1.5, ABHC-2 compared to ABHC-0.5, which was due to the fact that the porous structure was damaged by an excessive activating agent. The results of this study provided a predictive insight in view of optimizing process parameters and establishing the meaningful relationship between biochar porous structure and its resulting composites.

[Effect of Biochar Structure on Adsorption Characteristics of Ammonia Nitrogen].

Ammonia inhibition is a common phenomenon in biogas engineering which is rich in organic nitrogen substrate. Ammonia nitrogen in anaerobic digestate slurry can be fixed by biochar adsorption. Biochar is prepared from corn stalks and rice husks as raw materials at different temperatures (350℃, 450℃, and 550℃). The purpose is to explore the correlation between the physical and chemical structure of biochar and the adsorption characteristics of ammonia nitrogen. The structure and physicochemical properties of biochar were analyzed by elemental analysis, FTIR, BET, etc., and batch adsorption experiments were conducted to investigate the effect of biochar with different physicochemical properties on adsorption characteristics of ammonia nitrogen. The results indicated that the carbon and ash content in biochar increases with an increase in pyrolysis temperature; the NH4+-N adsorption of the corn stalk biochar prepared at 450℃ (CS450) and the rice husk biochar prepared at 550℃ (RH550) follows the quasi-secondary-and quasi-first-order kinetic models. The Freundlich adsorption model can better describe the isothermal adsorption process of ammonia nitrogen in CS450 and RH550 biochar. The adsorption capacity of corn straw carbon correlated strongly with its surface functional groups. The most significant correlation with the adsorption capacity of rice husk carbon is the specific surface area of biochar, followed by surface functional groups, and finally ash content. Among them, RH550 had the best adsorption performance, and the maximum adsorption capacity was 12.16 mg·g-1.

Characteristics of Corn Stover Components Pyrolysis at Low Temperature Based on Detergent Fibers.

In order to study the effect of biomass components on the low temperature (30-400°C) pyrolysis, the thermogravimetric analysis (TGA) of corn stover (CS) and its three detergent fibers (extracted by Van Soest method) were studied, and the model compounds of cellulose, hemicellulose and lignin were also tested as comparison. The results shows the low temperature pyrolysis index (P) is significantly different (PADL < Plignin < PCS < PNDF-CS < Pxylan < PADF-CS < Pcellulose). Klason-lignin has stronger thermal stability and decomposes more difficult than alkali lignin. The original cross-linked structure and interaction of the three components inhibited volatiles releasing, especially significant below 300°C. The synergistic effect between cellulose and lignin promoted devolatilization and decreased the initial temperature of cellulose decomposition. At last, the low temperature pyrolysis kinetics parameters (apparent activation energy and pre-exponential factor) of CS and its detergent fibers were calculated via the Coats-Redfern methods. This study can provide a theoretical basis for optimization of process conditions and industrial application of low temperature pyrolysis for lignocellulosic biomass.

Comparative study on fast pyrolysis of agricultural straw residues based on heat carrier circulation heating.

Fast pyrolysis of agricultural straw residues based on ceramic ball circulation heating was studied by using an originally developed V-shaped drop tube pyrolysis unit. The yields of bio-oil, bio-char and pyrolysis gas from these straw residues were in the range of 41-46, 26-30 and 26-29 wt%, respectively, with maize straw giving the highest bio-oil yield. A quadratic model was developed to correlate the cellulose-to-lignin-ratio (CLR) and hemicellulose-to-lignin-ratio (HLR) with bio-oil yield. For a given HLR above 1.12, the bio-oil yield continued to increase as the CLR increased. However, when the HLR was between 0.86 and 1.12, it tended to decrease first and then increase with the increase of CLR. In contrast with CS, the proportions of acids and ketones in the bio-oils increased by 13.3% and 14.8% for MS and 9.2% and 30.5% for WS, respectively, while the proportion of phenols decreased by 9.9% and 14.3%.

Catalytic pyrolysis of lignin in a cascade dual-catalyst system of modified red mud and HZSM-5 for aromatic hydrocarbon production.

Catalytic pyrolysis of lignin over a dual-catalyst system of modified red mud and HZSM-5 was carried out in a bench-scale micro-reactor. Effects of pyrolysis temperature, modified red mud to HZSM-5 ratio, catalysts to lignin ratio on the yield of products and selectivity of aromatic hydrocarbons were investigated. Results indicated that 550 °C was the optimal pyrolysis temperature with the maximal yield of bio-oil (20.16 wt%). At a modified red mud to HZSM-5 ratio of 1:1, the content of monocyclic aromatic hydrocarbons (MAHs) increased to 41.27% whereas that of polycyclic aromatic hydrocarbons (PAHs) decreased to 22.65%. Likewise, at a catalysts to lignin ratio of 2:1, a higher content of MAHs was produced with a decreased content of PAHs. The cascade dual-catalyst system may serve as an efficient approach to disposing lignin and red mud wastes with significant environmental impact. Besides, this study provides a solution for the valorization of lignin-rich resources.